As radiation monitoring and protection become an increasingly important issue, the growth in the scale of routine dosimetry is inevitable. A well established and widely employed dosimetry technique is thermoluminescence dosimetry (TLD) using LiF as the host material. U.S. Pat. No. 5,065,031 describes a representative multi-element TL dosimeter together with a dose calculation method which were designed to enable users to meet the ever growing demands of modern personnel dosimetry and also environmental monitoring. The therein described dosimeter is composed of two parts, namely a TLD card and a holder. The TLD card includes multiple thermoluminescent (TL) elements and the holder includes associated tissue equivalent radiation modifying filters.
Dose information is generally extracted from the integral area under the glow curve or part of the glow curve. Errors in such measurements may arise from the existence of background and the complex nature of fast-fading glow peaks. Much effort has been devoted to improving the accuracy of dose measurement by subtracting background signal and by eliminating contributions from the fast-fading glow peaks.
In routine dosimetry, where accuracy is not a critical issue, dosimetric information is, for practical reasons, approximated by the total area under the glow curve. The validity of such practice is ensured by carefully examining each individual glow curve and eliminating spurious readings before they can be used in dose algorithms, as discussed in Moscovitch, M., Chamberlain, J. and Velbeck, K. J., Dose Determination Algorithm for a Nearly Tissue-equivalent Multi-element Thermoluminescent Dosimeter, In: Proc. 2nd Conf. on Radiation Protection and Dosimetry, Orlando, Fla. ORNL/TM-1097, pp. 48-59 (1988).
Currently glow curve screening is predominantly done manually. This is not only time consuming, but also highly subjective in the pass/fail decision making. Existing analysis programs can not help change this situation because many features of the underlying methods are not compatible with the practical requirements of routine dosimetry.
For example, intrinsic glow curve characteristics, i.e., the location of the main glow peak and its width, are adversely affected by a host of factors such as the chip thickness, electronics of the card-reading instrument, and heating profile used for the readout. If all cards in a group are of the same type and are read in a relatively short time frame (say, one day) by the same reader, one can reasonably expect these glow curves to exhibit keen proximity in shapes. The expected or established values of these parameters are herein referred to as the "glow curve standards". Because these glow curve standards are largely determined by factors that are different from user to user, it is impossible to arrive at a universal set of parameters that are applicable to all users.